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1. Dec 5, 2014

Since C is constant, so all matter of equal rest mass have the same E ?!
e.g. an equal rest mass of water and rest mass of Uranium have the same energy ?

2. Dec 5, 2014

### Orodruin

Staff Emeritus
Yes, the mass energy related to 1 kg of water is the same as the mass energy in 1 kg of uranium.

3. Dec 5, 2014

### Staff: Mentor

Assuming the matter is at rest, yes. For matter in motion, $E = mc^2$ is not correct; the correct formula is $E^2 = m^2 c^4 + p^2 c^2$, where $p$ is the momentum. So pieces of matter with the same $m$ but different $p$ (because they are moving at different speeds) will have different $E$.